1. Field of Invention
The present invention relates in general to an electrostatic discharge (ESD) protection circuit. More particularly, the invention relates to an ESD protection circuit for a charge pump integrated in an LCD panel, and an electronic device and system using the same.
2. Description of Related Art
For commercial consideration, circuits are integrated together to reduce the total device size and production cost. However, as circuits are integrated together, problem arise with discharging electrostatic charge.
ESD protection circuits are commonly used to preventing the circuit from being damaged by discharging electrostatic charges. Generally, ESD protection circuits are applied on a signal I/O pad/pin that receives or outputs signals. Referring to FIG. 1, an exemplary ESD protection circuit is presented. As shown in FIG. 1, VDD and VSS are power sources in the electronic device 10, and each of the signal pins 100, 110, and 120 are connected to an ESD protection circuit 130, 140 and 150, respectively. Generally, ESD protection circuits are connected between the power sources VDD and VSS. For example, ESD protection circuit 130 has two diodes 132 and 134. Diode 132 is reversely connected between VSS and signal pin 100, and diode 134 is reversely connected between VDD and signal pin 100. By using the ESD protection circuit 130, the discharged electrostatic charges from signal pin 100 are released to VDD or VSS via diode 134 or 132, respectively.
However, the ESD protection circuit shown in FIG. 1 could not be used for a charge pump because a signal I/O pin may output or receive a voltage either higher than VDD or lower than VSS. The diodes in the ESD protection circuit are engaged when the received or output voltage is higher than VDD or lower than VSS. This results in abnormal operation of the ESD protection circuit.